1. Field of the Invention
The present invention relates to a medicine applying tool that is used while mounted on the tip of a catheter, for the purpose of treating various diseases such as thrombosis and arteriosclerosis, and for the treatment of re-occlusion after, for instance, PTCA. In particular, the invention relates to a medicine applying tool that utilizes a combination of ultrasonic waves and electrophoresis.
2. Description of the Prior Art
For example, myocardinal infarct is a disease in which blood flow is restricted by a thrombus or due to arteriosclerosis, so that heart muscles are not supplied with sufficient oxygen and may become necrotic.
Among the treatments for myocardinal infarct is the drug thrombolytic therapy, which is intended to dissolve a thrombus by means of oral application or intravascular injection of a medicine. However, in drug thrombolytic therapy, the medicine is supplied to the affected part by first having the medicine absorbed into the blood and then having the blood circulate through the body. Only a very small amount of the medicine used is absorbed by the affected part. Thus, drug thrombolytic therapy has a problem in that the efficiency in applying a medicine to an affected part is very low. It has a further problem in that the increasing of the density of the medicine to obtain its effective concentration in the blood may cause side effects in other organs.
On the other hand, among the treatments in which a part including a thrombus is treated in a concentrated manner is artery expanding therapy, which is also called PTCA (percutaneous transluminal coronary angioplasty). In the PTCA, a guide catheter is percutaneously introduced to the inlet of the coronary arteries of a patient through a portion of his thigh under X-rays, and then a catheter with a balloon at its tip is introduced, guided by the guide wire, to the part including a pathological change. In this state, the stricture of the coronary artery is relieved by expanding the balloon, to thereby increase the blood flow there.
However, artery expanding therapy has a problem that the probability of restenosis occurring several months after the operation is as high as 30% to 50%. Therefore, reexamination is performed by coronary angiography a predetermined period after the operation. If restenosis is found in the reexamination, the artery expanding therapy is performed again. If the restenosis is not cured, a coronary artery bypass operation is needed, which is much larger in scale.
Further, to prevent restenosis, during artery expanding therapy, a mesh-like cylindrical body called a stent is inserted into the stricture portion of the artery to reinforce the artery wall and the diameter of the cylindrical body is increased by expanding the balloon. However, even in this case, restenosis occurs at a very high frequency.